The present disclosure generally relates to a process for manufacturing semiconductor structures, and particularly to an image transfer process employing a hard mask layer to memorize a composite pattern, and structures for effecting the same.
A trilayer lithography process as known in the art employs an organic material layer such as an amorphous carbon layer in order to transfer a composite image of two independent images. The sidewalls of the organic material layer are formed with a significant level of line edge roughness and line width roughness during a pattern transfer etch that forms a pattern in the organic material layer employing an overlying layer as a patterned mask because the organic material layer is prone to lateral etching. The line edge roughness and the line width roughness of the organic material layer are further increased during a subsequent pattern transfer etch that transfers the pattern in the organic material layer into an underlying layer employing the organic material layer as an etch mask. The increased line edge roughness and line width roughness in the organic material layer is at least partly transferred into the underlying layer. Thus, the fidelity of pattern transfer is degraded due to the lateral etching of the organic material layer in the material stack employed for the trilayer lithography process.